Phthalocyanines with peripheral siloxane substitution

ABSTRACT

The present invention is phthalocyanine compounds with peripheral siloxane substitution, as well as methods for making these compounds and various uses thereof, having the basic structure: 
                         
wherein
         —W—X—Y—Z are peripheral groups comprising individual W, X, Y, and Z subgroups;   W is a linkage represented by the formula: —D—(R 1 ) 0.1 —, where D═S or O;   X is: —(CH 2 ) n —, n=2 to 8;   Y is a siloxane chain;   Z is an aryl or alkyl terminal cap;   M is two protons or a metal ion;
 
and forms a transparent film of high optical quality with large nonlinear absorption and thermal refraction, free of scattering from solid or liquid crystalline domains making them highly suitable for use as the active component in thin films protective eye wear, and optical data storage applications.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to new compounds that are a combination ofcovalently linked phthalocyanine and linear siloxane polymericstructures having a unique and novel combination of optical andTheological properties which are useful in protective eye wear,nonlinear optical devices and for optical data storage applications.

2. Description of the Related Art

Previously developed phthalocyanine materials have not possessed thehandling and processing characteristics of a single-component fluidcoupled with an optical transparency, nonlinear optical absorption andrefraction, chemical stability and moisture resistance. These aredesirable characteristics for use as thin films in nonlinear optical andoptical recording applications. Known methods for preparingphthalocyanines as thin films include vacuum deposition (sublimation,molecular beam, laser desorption), spraying or casting of a finesuspension or solution, Langmuir-Blodgett transfer, mechanical abrasion,and dispersion in a binder. The transparent thin film is a highlydesirable physical form for these materials as it allows utilization ofthe chromophore in optical applications such as optical limiting andoptical recording media which typically involve a material response toirradiation with a laser.

The deposition method, optical quality, and stability of aphthalocyaninefilm are determined by the molecular structure and properties of thematerial. Without peripheral substituents, phthalocyanine compounds aremicrocrystalline and relatively insoluble. Thin film preparation byvacuum deposition or high pressure abrasive techniques must frequentlybe accompanied by high temperatures. The microcrystalline character andthe presence of different crystalline polymorphs contribute to opticalscattering. These effects diminish the transparency of thephthalocyanine film. Temperature variation and exposure to chemicalvapors (including water) causes conversions between differentcrystalline forms further diminishing the quality of the film. (See M.S. Mindorff and D. E. Brodie, Can. J. Phys., 59, 249 (1981); F. Iwatsu,T. Kobayashi and N. Uyeda, J. Phys. Chem., 84, 3223 (1980); F. W.Karasek and J. C. Decius, J. Am. Chem. Soc., 74, 4716 (1952)).

When peripheral substituents are bonded to the phthalocyanine, molecularpacking efficiency and crystallinity are reduced, and the resultantmaterials may be soluble in a variety of solvents. Film formingtechniques involving the use of solvents, such as simple evaporationmethods and Langmuir-Blodgett transfer techniques, are feasibleprocessing methods. However, many peripherally substitutedphthalocyanines do not form films of good transparent optical quality.The peripheral groups need to be large in size and preferably of mixedisomer substitution to be effective. While crystalline packing ishindered by the presence of peripheral substituents, there are strongattractive van der Waal forces at work between the planar faces ofphthalocyanine rings which result in the constituent moleculesaggregating into ordered domains. These domains, if large enough, causeoptical scattering which strongly deteriorates the transparency andoptical quality of thin films. (See T. Kobayashi, in Crystals: GrowthProperties and Applications, N. Karl, editor, Springer-Verlag, NY, Vol13 (1991) pp. 1-63; A. Yamashita and T. Hayashi, Adv. Mater., 8, 791(1996)).

The interaction between adjacent phthalocyanine rings in an aggregatealso results in a strong electronic perturbation of the molecularstructure and a broadening of its absorption in the visible spectrum.This interaction in many cases detracts from the sought after nonlinearoptical properties. (See S. R. Flom, J. S. Shirk, J. R. Lindle, F. J.Bartoli, Z. H. Kafafi, R. G. S. Pong and A. W. Snow, in Materials Res.Soc. Proc., Vol. 247, (1992) pp 271-276).

Control of phthalocyanine aggregation is important first to reduce theordered domain size below a threshold where optical scattering occursand second to reduce the pertubation of the phthalocyanine electronicstructure to a level where spectral broadening and excited statelifetime shortening do not seriously diminish the nonlinear opticalabsorption of the phthalocyanine chromophore. The former is criticalsince optical transparency is required for a device of the currentinvention to function. For sufficient control of optical scattering, theordered molecular domain size must be smaller than the light wavelengthof application interest (usually in the 350 to 1500 nm range). Thelatter is less critical, but significant improvement in nonlinearoptical properties can be realized if aggregation can be reduced todimer formation or less.

Aggregation can be totally eliminated by blocking the co-facial approachof phthalocyanine rings by axial substitution onto metal ions complexedin the phthalocyanine cavity. (See N. B. McKeown, J. Mater. Chem., 10,1979 (2000); M. Brewis, G. J. Clarkson, V. Goddard, M. Helliwell, A. M.Holder and N. B. McKeown, Angew. Chem. Int. Ed., 37, 1092 (1998); A. R.Kane, J. F. Sullivan, D. H. Kenny and M. E. Kenney, Inorg. Chem., 9,1445 (1970)). However, this approach is limited to a small number oftetravalent octahedrally coordinating metals such as silicon. Forreasons discussed below, the nonlinear optical properties of this smallgroup of metallophthalocyanines are not particularly useful. (See H. S.Nalwa and J. S. Shirk, in Phthalocyanines: Properties and Applications,C. C. Leznoff and A. B. P. Lever, editors, VCH Publishers, Inc., NewYork (1996) Ch. 3).

Another approach to aggregation control is to utilize very largeperipheral substituent groups that hinder the co-facial approach ofphthalocyanine rings. Classes of such peripheral substituents areflexible oligomers (see D. Guillon, P. Weber, A. Skoulios, C. Piechockiand J. Simon, Molec. Cryst. Liq. Cryst., 130, 223 (1985); P. G.Schouten, J. M. Warman, M. P. Dehaas, C. F. van Nostrum, G. H. Gelineck,R. J. M. Nolte, M. J. Copvyn, J. W. Zwikker, M. K. Engel, M. Hannack, Y.H. Chang and W. T. Ford, J. Am. Chem. Soc., 116, 6880 (1994)),dendrimers (see M. Kimura, K. Nakada, Y., Chem. Comm., 1997, 1215; M.Brewis, B. M. Hassan, H. Li, S. Makhseed, N. B. McKeown and N. Thompson,J. Porphyrins Phthalocyanines, 4, 460 (2000); M. Brewis, M. Helliwell,N. B. McKeown, S. Reynolds and A Shawcross, Tetrahedron Lett., 42, 813(2000)), and capping groups (see D. D. Dominguez, A. W. Snow, J. S.Shirk and R. G. S. Pong, J. Porphyrins and Phthalocyanines, 5, 582(2001)). Examples of these three types of peripheral groups have hadlimited success in reducing aggregation. In many cases where the largeperipheral groups have significant structural symmetry and uniformity ofsize, liquid crystal formation with its consequent optical scatteringhas resulted. (See N. B. McKeown, Phthalocyanine Materials: Synthesis,Structure and Function, Cambridge University Press, Edinburgh (1998) pp.62-86). The liquid crystallinity has been avoided by utilizingperipheral groups with irregular symmetry combined with hydrogen bondingfunctional groups (see R. D. George and A. W. Snow, Chem. Mater., 6,1587 (1994)) or using a polydispersity of peripheral group chain lengths(see A. W. Snow, J. S. Shirk and R. G. S. Pong, J. PorphyrinsPhthalocyanines, 4, 518 (2000)). In the former case an epoxy-aminechemistry was utilized and a non-birefringent organic glass wasobtained, while in the latter case polyethylene oxide chemistry wasemployed and an isotropic liquid was obtained. The organic glass orliquid has very favorable melt processing characteristics.

Another requirement on the nature of the peripheral group is that itmust be chemically inert toward the metal ions complexed in thephthalocyanine cavity. Many of the metal ions that instill very usefulnonlinear optical properties to the phthalocyanine chromophore aremoderately labile and may be removed from the phthalocyanine cavity bycompeting complexing agents. This is particularly true of the heavymetal ions. In previous work with phthalocyanine compounds havingpolyethylene oxide peripheral groups, it was found that the ethyleneoxide structure was a strong enough competitor in complexing with a leadion and remove it from the phthalocyanine cavity (E. M. Maya, A. W.Snow, J. S. Shirk, S. R. Flom, R. G. S. Pong and G. L. Roberts,“Silicone Substituted Phthalocyanines for Optical Limiting Applications”presented at 221st National American Chemical Society Meeting, SanDiego, Calif., Apr. 5, 2001). To be useful for the current invention,the peripheral groups must not behave in this manner.

Regarding specific instances of tethering a siloxane group to aperipheral site of a phthalocyanine compound, only one example is known(U.S. Pat. No. 3,963,744). In this instance, the siloxane group is atris(trimethylsiloxy)silylalkyl structure which is connected through analkylsulfamide linkage to the phthalocyanine periphery. This material isclaimed to be compatible with cross-linked silicone polymers for thepurpose of acting as a dye or a pigment. Thistris(trimethylsiloxy)silylalkyl structure is compact (highly branchedwith short-chains) and nonlinear. A compound with these characteristicsdoes not form useful transparent thin films. Conversely, the presentinvention teaches linear polysiloxane structures. This linear quality isa critical feature in thin film processing and nonlinear opticalproperty enhancement.

Finally, the nonlinear optical properties of phthalocyanine materialsare strongly dependent on the identity of the species complexed withinits cavity. While this species may range from two protons to a widevariety of transition and main group metal ions, phthalocyanines withcomplexed heavy metal ions such as tin, bismuth, mercury, indium,tellurium, and particularly lead display the strongest nonlinear opticalproperties (see U.S. Pat. No. 5,805,326; H. S. Nalwa and J. S. Shirk, inPhthalocyanines: Properties and Applications, Vol. 4, C. C. Leznoff andA. B. P. Lever, editors, VCH Publishers, Inc., New York (1996) Ch. 3).In the divalent state, these metal ions do not coordinate to axialligands. Thus, such ligands cannot be utilized to block aggregation.Many of these metal ions are labile and can be easily displaced bycompeting chelating structures. This problem is particularly acute withthe polyethylene oxide structure where the oxygen sites in this polymerchain coordinate with the metal ion resulting in its consequent removalfrom the phthalocyanine cavity and diminishment of nonlinear opticalproperties.

SUMMARY OF THE INVENTION

Accordingly, one objective of the present invention is to provide amodified phthalocyanine that forms a transparent film of high opticalquality, free of scattering from solid or liquid crystalline domains.

Another objective of the present invention is to provide aphthalocyanine material that has been modified so that it is processableas an isotropic liquid or glass. Such processing includes: fillingconfined very small spaces (0.01 to 100 micron) by capillary action;mechanically producing a film by shearing between two flat surfaces; andcasting a film by solvent evaporation.

A further objective of the present invention is to producephthalocyanine films that display large nonlinear optical absorptionssuitable for use in optical limiting applications.

A further objective of the present invention is to producephthalocyanine films that have a large nonlinear thermal refraction tocomplement the nonlinear photochemistry in optical limitingapplications.

A further objective of the present invention is to provide aphthalocyanine material that has been modified so that it is useful inthe following applications: as a protective element in an opticallimiting component of direct view optical goggles, periscopes, gunsights, and binoculars; as the active element in laser intensity controland passive laser intensity noise reduction devices; as an opticalswitching element in an optical communications circuit; and as acomponent in compact disks, DVD's, optical cache memories, andholographic memories.

These and other objectives of the present invention are accomplishedthrough covalent bonding of siloxane oligomer structures of appropriatenumber, chain length and size distribution to connecting sites at theperiphery of the phthalocyanine ring structure and by complexation ofappropriate heavy metal ions in the phthalocyanine cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention will be readily obtainedby reference to the following Detailed Description of the PreferredEmbodiments' section and these drawings.

FIG. 1 is a graph showing the nonlinear transmission and opticallimiting of a 4.2 μm thick sample of pure liquid PbPc(PDMS₁₀)₄.

FIG. 2 is a graph depicting the increase in optical density as afunction of wavelength for PbPc(PDMS₁₀)₄ after visible excitation.

FIG. 3 is a graph demonstrating the optical limiting in f/5 optics for a4.2 μm thick sample of pure liquid PbPc(PDMS₁₀)₄.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Silicones have unique and useful properties as fluids and rubbers.Phthalocyanines have unique properties for optical and electronicapplications. Due to mutual incompatibility of silicones andphthalocyanines, a combination of the unique and useful propertiesdescribed above cannot be achieved by simply blending these materials.However, this invention achieves a coupling of silicones andphthalocyanine rings via covalent bonding into a single molecularsubstance which results in a unique combination of the useful propertiesof each component. There are alternative methods described herein forachieving this coupling of silicone chains to phthalocyanine rings.

The phthalocyanine material of the subject invention is described by thegeneral structural formula below. The central phthalocyaninesubstructure is the chromophore wherein resides the nonlinear opticalabsorption of visible light. Critical features to the general structurethat control this and other important material properties are the natureof the W, X, Y, Z peripheral group substructures and the species Mcomplexed in the cavity.

X = —(CH₂)_(n)— n = 2,3,4,5,6,7,8

M = Any metal; preferrably Pb, Sn, In, Tl, Zn, Cd, Hg and Bi; mostperferrably Pb

In the phthalocyanine structure, the numbered positions on the benzoring substructures indicate the peripheral positions where the group(s)W, X, Y, and Z may be covalently bonded. Each of the four benzo ringsubstructures may accommodate 0, 1 or 2 W—X—Y-Z substituents with thepreferred arrangement being one W—X—Y-Z substituent on each benzo ringsubstructure. There are four possible positions for peripheralsubstitution on each of the benzo ring substructures. All combinationsare practicable, but the preferred arrangements are those of lowsymmetry so that the phthalocyanine compound is a mixture of geometricisomers. This mixed isomer character is more effective in inhibitingcrystalline packed arrangements.

The peripheral group W—X—Y-Z is composed of four subunits with eachhaving possible structural variations. The variations are primarilydetermined by the synthetic route used in preparing the phthalocyanineas described below, and the preferred arrangements are determined byboth the facility of the synthesis route as well as the desired physicalproperties.

The W component of the group W—X—Y-Z is an ether or thioether linkage,and is either diaryl or arylalkyl. This is determined by the nitrodisplacement nucleophilic aromatic substitution reaction in thesynthesis in which a phenol or an alcohol or corresponding sulphuranalog may be used. The diaryl ether or thioether linkage is preferredbecause it has better photoxidative stability. When the phenol orthiophenol is used to make the diaryl linkage, there are three possiblelinkage sites on the phenylene group (1′, 2′, 3′ or ortho, meta and pararespectively) to which the X subgroup is bonded. While all as well asmixtures are practicable, the 1′ (or ortho) position is preferred. Thisoccurs for synthesis as well as property reasons. Substitution at theortho position causes the W—X—Y-Z group to turn back toward the face ofthe phthalocyanine ring resulting in a steric hindrance caused bycofacial aggregation. This mechanism for depressing aggregation has ahighly desirable effect on the nonlinear optical properties.

The X component is a variable length alkane chain. Its presence resultsfrom the hydrosilylation coupling reaction between a terminal olefin anda silylhydride terminated siloxane. In principle, an alkane of any chainlength may perform this function and variations incorporating chainbranching or heteroatoms are workable. The preferred structure forsubgroup X is a short chain length with the optimum preference being atrimethylene group. This group is the most synthetically facile. Itsshort chain length also has a minimal diluting effect on the thermalrefractive optical property associated with the silicone structure(subgroup Y).

The Y component is a siloxane chain of variable length. Thissubstructure is responsible for the liquid or glassy character of thephthalocyanine material and for the exceptionally large thermalrefractive nonlinear optical effect. There are three important variableswithin this substructure: the length, m, of the siloxane chain, thedispersity of the siloxane chain length, and the identity of the pendentgroup B. The siloxane chain length correlates with the glass transitiontemperature (Tg) and determines whether the material will be a glass ora liquid. Very short chains (3 or 4 units) correlate with a Tg aboveambient, while longer ones (>6 units) depress the Tg below roomtemperature. For liquid phthalocyanine materials, the viscositycorrelates with the siloxane chain length; initially decreasing withincreasing chain length in opposition to the influence of thephthalocyanine substructure, then increasing with further chain lengthreflecting the effect of the siloxane molecular weight. The longer thechain length (the greater the volume fraction of the Y component), themore this phthalocyanine material's rheology and morphology resemble thepure siloxane material. The longer chain lengths also reducephthalocyanine aggregating tendency by steric hindrance. However, thephthalocyanine structure's volume fraction must remain significant (inthe approximate range from a high of 25% to a low of 1%, whichcorrelates with a siloxane chain length between 3 and 100) if thenonlinear optical properties associated with this chromophore are to beutilized in a thin film physical form. In general, the preferred chainlengths range from 7 to 28 units. A polydispersity of siloxane chainlength is a variation about an average chain length. While the currentinvention may be practiced with either a monodisperse or polydispersesiloxane chain, polydispersity is beneficial in that its breadth reducesa tendency for organized molecular packing which may result in liquidcrystal formation. The synthesis method for preparation of thesilylhydride terminated siloxane intermediates yields a polydisperseproduct, utilized without fractionation in the current invention.

The identity of the pendant group B on the siloxane chain is a veryimportant variable in that this feature offers a method of controllingthe refractive index of the phthalocyanine material. The preferredidentity is methyl for reasons of availability of precursors, synthesisfacility and associated useful optical, physical and processingproperties. However, the phthalocyanine material refractive index may beeither increased or decreased by substituting the phenyl or3,3,3-trifluoropropyl respectively for the methyl group in a fraction orall of the pendant B groups.

The Z component is a terminal or capping group on the free end of thesiloxane chain. It is typically an inert alkyl group from the alkyllithium initiator used in preparing the siloxane polymer from the cyclictrimer by anionic polymerization. This is the preferred embodiment as itconfers a long term stability and processability to the phthalocyaninematerial. However, this terminal group may also be a reactive functionalgroup such as a silylhydride. In this case, the phthalocyanine compoundmay couple with other or similar functional groups to generate networkstructures. The phthalocyanine compound may also bond to surfaces byreaction of the silylhydride group.

The M component is either a metal ion or two protons. The identity ofthe metal ion has a very important influence on the nonlinear opticalabsorption of the phthalocyanine chromophore. Previous teaching (U.S.Pat. No. 5,805,326) has demonstrated that heavy metal ions, particularlylead, are the preferred embodiments. The invention will function withother metal ions as well as the two protons complexed in thephthalocyanine cavity although the efficiency in the optical limitingapplication is not as high.

The synthesis of phthalocyanine compounds is well known to those skilledin the art. The following references provide a comprehensive review: D.Whole, G. Schnurpfeil and G. Knothe, Dyes and Pigments, 18, 91-102(1992); A. B. P. Lever, Advances in Inorganic and Radiochemistry, 58,27-114(1965); C. C. Leznoff and A B. P. Lever (editors),Phthalocyanines: Properties and Applications, VCH Publishers, Inc., Vol.1 (1989); F. H. Moser and A. L. Thomas, The Phthalocyanines, CRC Press,Inc., Vols. 1 and 2 (1983); B. D. Berezin, Coordination Compounds ofPorphyrins and Phthalocyanines, John Wiley & Sons (1981); N. B. McKeown,Phthalocyanine Materials: Synthesis, Structure and Function, CambridgeUniversity Press (1998). Specific details form any particularphthalocyanine compounds may be found in the many articles cited by theabove reviews.

The phthalocyanine materials of the subject invention are unique in thatlinear siloxane polymers are tethered to the periphery of thephthalocyanine structure to obtain very novel and useful properties(i.e. intrinsic liquid character, large refractive index—temperaturedependence, isotropic thin film formation, and chemical inertness) thathave not been previously achieved by other peripherally bondedstructures. In the prior art, the only instance of tethering a siloxanegroup at the periphery of a phthalocyanine ring involved atris(trimethylsiloxy)silylalkyl group attached through a sulfamidelinkage to the phthalocyanine periphery (U.S. Pat. No. 3,963,744). Thishighly branched and very symmetrical group has a highly differentchemistry, synthesis method, properties and purpose from the linear longchain siloxane polymers used in the present invention.

The synthesis used in the present invention consists of a series ofreactions depicted below:

The first step is preparation of the silylhydride terminated siloxanepolymer, 3, by anionic polymerization of the cyclotrisiloxane, 2,following a published procedure (see A. T. Holohan, M. H. George, J. A.Barrie and D. G. Parker, Macromol. Chem. Phys., 195, 2965 (1994)). Thesiloxane chain length is determined by the monomer:alkyl lithiuminitiator molar ratio. The product distribution is narrow but notmonodisperse. The identity of the alkyl capping group, Z, is determinedby selection of alkyl lithium initiator. The silylhydride terminal groupis supplied by the dimethylchlorosilane termination reagent. The pendantgroup, B, may be an alkyl group, phenyl group or a haloalkyl group andis determined by selection of the cyclotrisiloxane monomer, 2.

The second step is preparation of the olefin terminated alkylsubstituted phthalonitrile intermediate, 6, by a nucleophllic aromaticnitro displacement reaction between the nitrophthalornitrile, 4, and theterminal olefin substituted alcohol or phenol, or corresponding sulphuranalog, 5. There are many possibilities for structural variation inthese reagents. The nitro group in 4 may be substituted at the 3- or4-position. Substitution at the 3-position has been shown to reduceaggregation tendency in the analog phthalocyanine compound (R. D.George, A. W. Snow, J. S. Shirk and W. R. Barger, J. Porphyrins andPhthalocyanines, 2, 1-7 (1998)). For reagent 5, a terminal olefinsubstituted alkylphenol or alkylthiophenol is the preferred embodiment.The use of terminal olefin substituted alcohols, such as allyl alcohol,is practicable, however, the reaction yields are lower and thephthalocyanine analog compound has less stability compared with usingthe phenol. While practically any phenol or thiophenol with an olefinterminated alkyl substituent is preferred, a most preferred embodimentfor reagent 5 is 2-allylphenol. This precursor is readily available,synthesis yields are good, phthalocyanine analog stability is good, andphthalocyanine aggregation tendency is lowered. The volume fraction ofthis hydrocarbon linkage substructure is significantly lower whencompared with using phenols with larger olefin terminated alkyl groups.Details of the preparation of this 4-(2-allylphenoxy)phthalonitrile keyintermediate are given in Example 1.

The third step is preparation of the polysiloxane substitutedphthalonitrile intermediate, 7, by a hydrosilylation coupling reactionbetween the olefin terminated phthalonitrile, 6, and the silylhydrideterminated siloxane polymer, 3. This reaction requires a trace amount ofa hydrosilylation catalyst, such as chloroplatinic acid. (see Examples 2and 3).

The fourth step is conversion of the siloxane substitutedphthalonitrile, 7, to the corresponding phthalocyanine, 1. Twofrequently used conditions employing hydroquinone (see A. W. Snow, N. P.Marullo, and J. R. Griffith, Macromolecules, 17, 1614 (1984)) or lithiumpentoxide (P. A. Barret, D. A. Frye, and RP P. Lindstead, J. Chem. Soc.,1938, 1157) as coreactants were not successful. The use of DBU(1,8-diazabicyclo[5.4.0]undec-7-ene) or dimethylaminoethanol/metal saltas the coreactants are practicable. However, the preferred route is touse lead (II) oxide as the coreactant. This yields the desired leadphthalocyanine, 1 M=Pb, is good yield (Examples 5 and 6). This leadphthalocyanine may be transformed to the corresponding metal-freephthalocyanine, 1 M=H₂, by treatment with a small amount of acid(Example 8). A wide variety of other metals may then be introduced intothe phthalocyanine cavity by treatment of the metal-free phthalocyaninewith a solution of a basic salt (e.g. an acetate) of the desired metal.

An alternate but less preferred synthetic route to the desired siloxanesubstituted phthalocyanine, 1, is to reverse the order of the third andfourth steps by converting the olefin terminated alkyl substitutedphthalonitrile intermediate, 6, to its corresponding tetraallylphenoxyphthalocyanine (Examples 4 and 7) then couple the silylhydrideterminated siloxane polymer, 3, to this tetraallylphenoxy phthalocyanineto yield the siloxane substituted phthalocyanine, 1, using a non-acidicheterogeneous catalyst, such as platinum-divinyl tetramethyldisiloxane.This route requires a large excess of the silylhydride terminatedsiloxane polymer, 3, in the final step to insure total functionalizationof the allylphenoxy phthalocyanine which makes the purification of thefinal compound much more difficult.

The polysiloxane substituted phthalocyanines of the current invention,with the peripheral group molecular structure falling within the rangesspecified for the W—X—Y-Z component of the general structure shownabove, display characteristics of a very high quality opticallytransparent film. Observations and physical measurements onphthalocyanine materials prepared in Examples 5, 6 and 8 verify thesecharacteristics. When these materials are examined under high opticalmagnification (600×) between crossed polarizers, no birefringence isobserved. This is a sensitive test to directly diagnose the existence ofvery small molecularly ordered anisotropic domains with liquid or solidcrystalline character. This observation is further supported by notingin the region of the optical spectrum where no phthalocyanine absorptionoccurs (900-1200 nm), the base line is virtually flat. As a furtherobservation, no visually observed scattered light when the film is underintense laser irradiation. This is a clear indication that thepolysiloxane peripheral groups are successful in prevention of formationof ordered domains whose dimension is comparable to the visible lightwavelength or larger.

Quantitative measurements have also been made on the dimerizationformation constant which is a parameter by which aggregating tendencycan be assessed. The results are presented in Table 1 for thepolysiloxane substituted phthalocyanine compounds of Examples 5(PbPc(PDMS₁₀)₄ and 8 (H₂Pc(PDMS₁₀)₄ along with comparative data for therespective cumylphenoxy substituted phthalocyanines (PbPc(CP)₄ andH₂Pc(CP)₄).

TABLE 1 Dimerization Formation Constants in Solution H₂Pc(CP)₄ K_(D) =7000 M⁻¹ H₂Pc(PDMS₁₀)₄ K_(D) = 31 M⁻¹ PbPc(CP)₄ K_(D) =  400 M⁻¹PbPc(PDMS₁₀)₄ K_(D) =  2 M⁻¹

These measurements clearly demonstrate that the polysiloxane substituentrelative to the cumylphenoxy hydrocarbon substituent reduces thetendency of the phthalocyanine to aggregate by a factor of at least 15in both the metal-free and lead substituted analogs.

Another very critical physical characteristic conferred on thephthalocyanine material by the polysiloxane peripheral group is that offacile processability. Depending on the glass transition temperature,this peripheral group renders the phthalocyanine an amorphous isotropicglass or liquid. As such these materials can be processed as melts bysimple application of heat to regulate the viscosity. Thephthalocyanines of the Examples 5, 6 and 8 have respective Tg's of 3, 10and −3° C. These materials are room temperature liquids and may beprocessed as thin films of very uniform and precisely controlledthickness by using capillary action to fill short pathlength (1 to 50micron) flat optical cells. Smaller confined spaces down to 0.01 micronmay also be filled by capillary action.

These polysiloxane phthalocyanines may also be processed by mechanicallyshearing a film between two optical surfaces. Alternately, thephthalocyanine materials of this invention are soluble in a variety ofsolvents and the simple generation of films by solvent casting orspraying and evaporation is a practicable technique. Blending thesephthalocyanines in polymers is another method of film preparation.

These polysiloxane substituted phthalocyanine materials display anenhanced nonlinear optical absorption attributable to the phthalocyaninechromophore and the species complexed within the cavity. A reversesaturable absorption mechanism has been assigned to this photochemistrywhere an electronic transition from a first excited state to a secondexcited state has a higher transition probability than from the groundstate to the first excited state. This transition from the first to thesecond excited state becomes the dominant transition once a thresholdpopulation is reached in the first excited state. To reach the criticalfirst excited state population threshold, this state must have asufficiently long lifetime. This long lifetime is promoted by havingheavy metal ions complexed in the phthalocyanine cavity and by a lowlevel of aggregation. Both the heavy metal ions and the polysiloxaneperipheral groups are important influences in the current invention.FIG. 1 displays nonlinear transmission and optical limiting data of a4.2 micron film of the phthalocyanine material of Example 5. Thesemeasurements were made at 532 nm using f/5 optics and an f/5 opticallimiter with a pulse width of 7±1 ns. The sample transmission at 532 nmwas 84%. The nonlinear transmission measurements give an approximateexcited state absorption cross-section of 1.0±0.2×10⁻¹⁶ cm² and a ratioof the excited state to ground state extinction coefficient of 36 atthis wavelength. This excited state absorption is larger than that foundin solutions of PbPc(CP)₄, a known superior optical limiter (U.S. Pat.No. 5,805,326). The relative difference in absorption coefficientsbetween the excited and ground states over a wavelength range of 430 to600 nm following excitation at 606 nm for the phthalocyanine material ofExample 5 is depicted in FIG. 2. This illustrates the wavelength windowover which this material will be an effective optical limiter. Thus,FIG. 1 illustrates the magnitude of limiting for a single wavelength,and FIG. 2 shows a breadth of wavelengths where limiting will beeffective.

In addition to the nonlinear optical absorption of the phthalocyaninechromophore, the polysiloxane peripheral group makes a furthercontribution to the optical limiting through its nonlinear thermalrefraction. A rapid change in refractive index with temperature, dn/dT,shifts the focal point of focused light and lowers the quantity of lightpassing through a series of focused optics. Because the phthalocyaninechromophore is very efficient in converting absorbed light to heat, amedium with a large refractive index response to heat will accentuatethis thermal refractive effect. The polysiloxane structure has a verylarge refractive index response to heat, and by virtue of being bondedto the periphery of the phthalocyanine ring is well-positioned toaccentuate this effect. The temperature dependence of the refractiveindex was measured for the polysiloxane phthalocyanine of Example 5 viaellipsometry to be −5.4±1×10⁻⁴° C.⁻¹ between 25 and 40° C. and anaverage dn/dT of −4±1×10⁻⁴° C.⁻¹ between 25 and 95° C. The latter valuecompares well with that found for linear polydimethylsiloxane liquids.Relative to other polymers, polydimethylsiloxane has an exceptionallylarge dn/dT. This thermal refractive enhancement to the optical limitingis depicted in FIG. 1 by comparing the optical limiting curve with thatattributable to the only the nonlinear optical absorption. FIG. 3 showsthe optical limiting measurements when carried to higher energies.

Other favorable properties that the polysiloxane peripheral groupsconfer on the phthalocyanine materials are chemical inertness andmoisture resistance. The heavy metal ions, particularly lead, are labileto displacement from the phthalocyanine cavity. Competing complexingagents and the presence acid and moisture promote this displacement. Asnoted in the prior art description section, peripheral groups withcoordination sites that will complex with a labile metal such as thepolyethylene oxide structure can play the role of a competing complexingagent. Water and/or a source of protons complete the conversion tometal-free phthalocyanine. The oxygen atoms in the polysiloxanestructure are very weak coordinating sites and are sterically hinderedby pendant groups attached to the siloxane chain. The polysiloxanestructure is also very hydrophobic. The lead phthalocyanine materialswith peripheral siloxane substitution in the present invention are lesslabile than other lead phthalocyanine materials toward conversion to themetal-free analog.

EXAMPLES

The examples which follow serve to illustrate the practice of thisinvention and quantify the physical properties but are in no wayintended to limit its application.

1. Synthesis and Characterization of Precursors

Example 1 Synthesis and Purification of4-(2-allylphenoxy)phthalonitrile(I)

In a nitrogen atmosphere, 6.37 g (0.046 mol) of finely groundedanhydrous K₂CO₃ was added to a solution of 3.89 g (0.029 mol) of2-allylphenol (Aldrich) and 5.02 g (0.029 mol) of 4-nitrophthalonitrile(Aldrich) in 25 mL of dry Me₂SO by 0.32 g additions at ½h intervals overan 6-h period. The mixture was stirred 24 hours at room temperatureunder nitrogen. The undissolved salt is filtered from the reactionmixture and the filtrate is dissolved in 100 mL of methylene chloride.The solution is extracted 5 times with 50 mL water. The organic phasewas dried over anhydrous magnesium sulfate, filtered and evaporated todryness. The crude product is dissolved in minimum of toluene andchromatographed on alumina with toluene elution. The toluene wasevaporated and the resulting oil vacuum dried to yield 5.28 g (70%) ofI. The oil turns into a solid in few days.

¹H-RMN (CDCl₃, 300 MHz) 3.23 (2H, d, CH₂), 4.95 (2H, dd, ═CH₂), 5.78(1H, m, ═CH), 6.95 (1H, d, Harom), 7.12-7.33 (5H, m, Harom), 7.68 (1H,d, Harom)ppm; ¹³C-RMN (CDCl₃, 75 MHz) 34.0, 108.5, 114.9 and 115.4(CN),116.7, 117.6, 120.8, 120.9, 121.0, 126.7, 128.5, 131.6, 132.4, 135.3,135.4, 151.1, 161.7 ppm; IR (NaCl) 3082 (═CH₂), 2229 (CN), 1615 (C═C),1595 and 1486 (C—C), 1246 cm⁻¹.

Example 2 Synthesis and Purification of4-(H₉C₄[Si(CH₃)₂O]₉Si(CH₃)₂(CH)₃C₆H₄O) Substituted phthalonitrile (II)

A mixture of 1 g (3.84 mmol) of 1 and 4 drops of a 0.1 N isopropanolsolution of H₂PtCl₆6H₂O (Aldrich) was heated at 60° C. Then 3 g (3.84mmol) of hydrosilyl terminated PDMS precursor(H₉C₄[Si(CH₃)₂O]₉Si(CH₃)₂H) (A. T. Holohan et al., Macromol. Chem. Phys.195, 2965(1994)) were added dropwise. The mixture was stirred at 60° C.for 1 h. The oil obtained was purified by silica column chromatographyusing toluene as eluent. The solvent was evaporated to yield 2.20 g(55%) of a colorless oil after vacuum dry.

Tg: 14° C.; n_(D)=1.4482; ¹H-RMN (CDCl₃, 300 Mz) 0.012-0.064 (60H, m,SiCH₃), 0.51 (4H, m, SiCH₂), 0.86 (3H, t, CH₃), 1.29 (4H, m, CH₂), 1.58(2H, m, CH₂), 2.49 (2H, t, CH₂), 6.95 (1H, d, Harom), 7.14-7.31 (5H, m,Harom), 7.68 (1H, d, Harom) ppm; IR (NaCl) 2966 (CH), 2229 (CN), 1602and 1492 (C—C), 1254 (SiCH₃), 1098 and 1033 (SiOSi), 806 (SiC) cm⁻¹.

Example 3 Synthesis and Purification of4-(H₉C₄[Si(CH₃)₂O]₁₈Si(CH₃)₂(CH₂)₃C₆H₄O) Substituted phthalonitrile(III)

The procedure is identical to that for example 2 except a longerhydrosilyl terminated PDMS precursor (H₉C₄[Si(CH₃)₂O]₁₈Si(CH₃)₂H) wasused, in the same stoichiometric relationship.

Tg: 10° C.; n_(D)=1.4318; ¹H-RMN (CDCl₃, 300 MH) 0.015-0.144 (114H, m,SiCH₃), 0.54 (4H, m, SiCH₂), 0.88 (3H, t, CH₃), 1.32 (4H, m, CH₂), 1.55(2H, m, CH₂), 2.50 (2H, t, CH₂), 6.95 (1H, d, Harom), 7.15-7.32 (5H, m,Harom), 7.70 (1H, d, Harom) ppm; IR (NaCl) 2966 (CH), 2235 (CN), 1608and 1492 (C—C), 1272 (SiCH₃), 1098 and 1033 (SiOSi), 800 (SiC) cm⁻¹.

2. Synthesis and Characterization of Lead Phtahlocyanines

The procedure for lead phthalocyanine (Pc) is very similar and analogousto those reported by Lindstead and coworkers for unsubstitutedmetallophthalocyanines. The general reaction and purification were asfollows except where departures are specified.

To a 10×75 mm tube fitted with a magnetic stirring bar were added thecorresponding prescribed quantities of dicyano precursor (I, II, or III)and lead oxide (Fisher, yellow). The mixture was carefully fused undervacuum (less than 0.1 torr) to remove residual solvents and air occludedin the dicyano precursor and sealed under vacuum. The entire tube washeated with stirring for the designed time and temperature. The crudeproduct was purified by column chromatography on silica (Fluka AG) usingtoluene as an elution solvent. The toluene was concentrated to yield agreen liquid chromophore which was dried under vacuum at 80° C. for 2 h.

When dicyano precursor I was used, a green solid phthalocyanine wasobtained which was purified by column chromatography on alumina (neutralBodman, activity 1).

Example 4 PbPc(2-allylphenoxy)₄ (Iv)

A mixture of 0.500 g (1.92 mmol) of I and 0.328 g (1.47 mmol) of PbO wasreacted at 180° C. for 12 hours. Yield: 0.261 g (42%); m.p.>250° C.;UV-vis (toluene) 721, 650, 346 nm; IR(NaCl) 3076 (═CH₂), 2919 (CH), 1638(C═C), 1608, 1485 (C—C), 1239 cm⁻¹.

Example 5 PbPc(OC₆H₄(CH₂)₃Si(CH₃)₂[OSi(CH₃)₂]₉C₄H₉)₄(V)

A mixture of 0.800 g (0.766 mmol) of II and 0.131 g (0.589 mmol) of PbOwas reacted at 180° C. for 12 hours. Yield: 0.512 g (61%); Tg: 3° C.;UV-vis (toluene) 721, 648, 365 nm; IR(NaCl) 2959 (CH), 1608 and 1492(C—C), 1253 (SiCH₃), 1091 and 1014 (SiOSi), 800 (SiC) cm⁻¹.Phthalocyanine V can also be prepared by hydrosilylation reaction overthe phthalocyanine IV. A mixture of 0.100 g (0.077 mmol) of IV and 8drops of Platinum divinyltetramethyldisiloxane complex in xylene (GelestInc) was dissolved in 2 mL of toluene and was heated at 60° C. Then0.481 g (0.616 mmol) of hydrosilyl terminated PDMS precursor(H₉C₄[Si(CH₃)₂O]₉Si(CH₃)₂H) were dropwise added. The mixture was stirredat 60° C. for 6 h. and purified in the same way.

Example 6 PbPc(OC₆H₄(CH₂)₃Si(CH₃)₂[OSi(CH₃)₂]₁₈C₄H₉)₄ (VI)

A mixture of 0.500 g (0.292 mmol) of III and 0.050 g (0.224 mmol) of PbOwas reacted at 180° C. for 12 hours. Yield: 0.226 g (44%); Tg: 10° C.;UV-vis (toluene) 719, 647, 389, 367 nm; v(NaCl) 2966 (CH), 1621 and 1486(C—C), 1266 (SiCH₃), 1091 and 1033 (SiOSi), 800 (SiC) cm⁻¹.

3. Synthesis and Characterization of Metal Free Phtahlocyanines

Example 7 H₂Pc(2-allylphenoxy)₄ (VII)

To a 10×75 mm tube fitted with a magnetic stirring bar were added 0.500g (1.92 mmol) of I and 0.052 g (0.48 mmol) of hydroquinone (Aldrich).The mixture was carefully fused under vacuum (less than 0.1 torr) toremove residual solvents occluded in the dicyano precursor and sealedunder vacuum. The entire tube was heated at 170° C. with stirring for 12h. The crude product was purified by column chromatography on alumina(neutral Bodman, activity 1) using toluene as an elution solvent. Thetoluene was concentrated and the blue solid obtained was dissolve in aminimum amount of chloroform, and the phthalocyanine was precipitated bydropwise addition of methanol. The product was collected and dried.Yield: 0.280 g (56%); m.p.>250° C.; UV-vis (toluene) 703, 667, 639, 605,350 nm; IR(NaCl)3295 (NH), 3075 (═CH₂), 1638 (CH═CH₂), 1611 and1467(C—C), 1228 cm⁻¹; ¹H-RMN (CDCl₃, 300 MHz)−4.1 (s, NH), 3.6 (m, CH₂),5.1 (m, ═CH₂), 6.1 (m, CH═), 6.8-7.7 (m, H-arom) ppm; m/z 1091.

Example 8 H₂Pc(OC₆H₄(CH₂)₃Si(CH₃)₂[OSi(CH₃)₂]₉C₄H₉)₄ (VIII)

Metal free phthalocyanine VIII was obtained by displacement of a leadion from the phthalocyanine (V).

To a solution of 0.300 g (0.068 mmol) of V in 10 mL of methylenechloride were added three drops of trifluoroacetic acid. The mixture wasstirred at room temperature for 10 min. The methylene chloride solutionwas extracted 3 times with 15 mL of 5% NaHCO₃. The organic phase wasdried over anhydrous magnesium sulfate, filtered and evaporated todryness. The crude product was purified by column chromatography onsilica (Fluka AG) using toluene as an elution solvent. The toluene wasconcentrated to yield a blue liquid which was dried under vacuum at 80°C. for 2 h. Yield: 0.160 mg (56%); Tg: 6° C.; UV-vis (toluene) 703, 666,638, 605, 346 nm; IR(NaCl) 3295 (NH), 2959 (CH), 1615 and 1479 (C—C),1259 (SiCH₃), 1091 and 1027 (SiOSi), 807 (SiC) cm⁻¹; m/z 4500-2200.

Compound VIII may also be prepared following a similar procedure tothose reported by O. Bekarôglu and co-workers (A. G. Gurek, O.Bekarôglu, J. Chem. Soc. Dalton Trans., 1994, 1419).

A mixture of 0.250 g (0.24 mmol) of II and 0.036 g (0,24 mmol) of DBU(1,8-diazabicyclo[5.4.0]undec-7-ene) (Aldrich) was dissolved in 2 mL ofpentan-1-ol. The mixture was stirred at 136° C. for 7 h. The solvent wasremoved by vacuum distillation and the crude was purified as above.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. Additional advantages andmodifications will readily occur to those skilled in the art. Therefore,the invention in its broader aspects is not limited to only the specificdetails and representative embodiments shown and described herein.Accordingly, various modifications may be made without departing fromthe spirit or scope of the general inventive concept as defined by theappended claims and their equivalents.

1. An optical limiter composition comprising a phthalocyanine compoundwith peripheral siloxane substitution on the benzo ring substructureshaving the structure:

wherein —W—X—Y—Z are peripheral groups comprising individual W, X, Y,and Z subgroups; wherein W is covalently bonded to any of the numberedpositions on the benzo ring substructures; wherein each of the benzoring substructures may have 0, 1, or 2 of the —W—X—Y—Z peripheralgroups; wherein W is a linkage represented by the formula:—D—(R¹)_(0,1)—; wherein D is an atom selected from the group consistingof sulphur and oxygen; and R¹ is a intermediary selected from the groupconsisting of aryl and alkyl hydrocarbons; wherein X is: —(CH₂)_(n)—;wherein n=2 to 8; wherein Y is a siloxane chain having the formula:

wherein m=3 to 100; and wherein B is a pendant substituent selected fromthe group consisting of —C_(p)H_(2p+1) where p=1 to 4; —C₆H₅;—CH₂CH₂CF₃; and combinations thereof wherein Z is a terminal cap on thefree end of the W—X—Y—Z peripheral groups selected from the groupconsisting of —H; linear alkyl group represented by the formula—C_(q)H_(2q+1) where q=1 to 8; branched alkyl group represented by theformula —C_(q)H_(2q+1) where q=1 to 8; and an aryl group; and wherein Mis two protons or a metal ion.
 2. The optical limiter composition ofclaim 1, wherein the phthalocyanine compound is used as an unconfinedthin film.
 3. The optical limiter composition of claim 1, wherein thephthalocyanine compound is used as a confined thin film.
 4. The opticallimiter composition of claim 1, wherein the phthalocyanine compound isused in a confined capillary array.
 5. A method for protecting eyes oran optically sensitive material comprising: using in an optical limitercomposition a phthalocyanine compound with peripheral siloxanesubstitution on the benzo ring substructures having the structure:

wherein —W—X—Y—Z are peripheral groups comprising individual W, X, Y,and Z subgroups; wherein W is covalently bonded to any of the numberedpositions on the benzo ring substructures; wherein each of the benzoring substructures may have 0, 1, or 2 of the —W—X—Y—Z peripheralgroups; wherein W is a linkage represented by the formula:-D-(R¹)_(0,1)—; wherein D is an atom selected from the group consistingof sulphur and oxygen; and R¹ is a intermediary selected from the groupconsisting of aryl and alkyl hydrocarbons; wherein X is: —(CH₂)_(n)—;wherein n=2 to 8; wherein Y is a siloxane chain having the formula:

wherein m=3 to 100; and wherein B is a pendant substituent selected fromthe group consisting of —C_(p)H_(2p+1) where p=1 to 4; —C₆H₅;—CH₂CH₂CF₃; and combinations thereof; wherein Z is a terminal cap on thefree end of the W—X—Y—Z peripheral groups selected from the groupconsisting of —H; linear alkyl group represented by the formula—C_(q)H_(2q+1) where q=1 to 8; branched alkyl group represented by theformula —C_(q)H_(2q+1) where q=1 to 8; and an aryl group; and wherein Mis two protons or a metal ion.
 6. The method of claim 5, wherein thephthalocyanine compound is used as an unconfined thin film.
 7. Themethod of claim 5, wherein the phthalocyanine compound is used as aconfined thin film.
 8. The method of claim 5, wherein the phthalocyaninecompound is used in a confined capillary array.